Magnetic slug switch



Apri! 2, 1968 5. RISK MAGNETIC SLUC- SWITCH Filed May 2, 1966 2 Sheets-Sheet 1 2 INVENTORY- GEORGE RISK WK M ATTORNEY April 2, 1968 MAGNETIC S-LUG SWITCH Filed May 2, 1966 2 Sheets-Sheet 2 INVENTOR: GEORGE RISK MR M ATTORNEY G. RISK 3,376,527

Unite States atent 3,376,527 MAGNETIC SLUG SWITGH Columbus, Nehru, assignor to Inc, Columbus, Nebn,

George Risk a corporation of This invention relates to a switch device for use in an electrical circuit. In particular this invention relates to a switch device that operates by means of a translatable magnetic slug for controlling the electrical current flow of the circuit, said translatable magnetic slug being appropriately repelled to switch the current by means of an external magnet having relative movement with respect to the translatable magnetic slug.

It is an object of the present invention to provide a switch device for use in an electrical circuit that is adaptable to various types and magnitudes of electrical current.

It is another object to provide a durable, long-lasting, and highly reliable switch device having a minimum of Wearable parts.

It is another object to provide a switch device having a freely-slidable e.g. a floating electrically-conductive bridge element for a plurality of distinctly separated electrical contacts, said bridge element having two distinct stations appropriate to make and break the electrical current flow between the plurality of electrical contacts.

It is yet another object to provide a means for unequivocally translating the fioating bridge element from one station to the other station and to provide an affirmatively disposed abutment of the bridge element when stationed against the contacts so as to prevent electrical arcing and burning of the abutting contacts and bridge element. It is a related object to provide a means for unequivocally translating the bridge element from its abuttable station with the electrical contacts to the other station remote of the electrical contacts to cleanly break the circuit without electrical arcing and burning of the contacts and bridge element.

It is a further object to provide a means for furnishing an inert sealed environment for the bridge element and the electrical contacts to provide an explosion-proof switch device.

It is a further object to provide a stabilizing means for the floating bridge element so that the magnetically operable switch device may be resistant to shock and vibrational forces.

It is yet another object of the present invention to provide a resilient electrical-conductive portion for the bridge element so as to insure effective operational abutment of said electrically-conductive portion between the distinctly separated contacts.

With the above and other objects and advantages in view, which will become apparent as the description proceeds, the invention comprises the novel form, combination and arrangement of parts as hereinafter more fully described, reference being :had to the accompanying drawing wherein like numbers refer to like parts in the several views and in which:

FIGURE 1 is a perspective view of a representative embodiment of the magnetically operable switch of the present invention.

FIGURE 2 is a sectional elevational view line 2-2 of FIGURE 1.

FIGURE 3 is a sectional plan view taken along line 3-3 of FIGURE 2.

FIGURE 4 is a sectional elevational view similar to that of FIGURE 2 of an alternate embodiment of the present invention.

taken along FIGURE 5 is a perspective view of an alternate sluglike bridging element having a resiliently attached electrically-conductive portion.

The magnetically operable switch of the present invention comprises a hollow tubular inner casing 10 having a relatively low magnetic permeability and having a longitudinal central axis 13, a first end 11, and a second end 12; a pair of distinctly separated electrical contacts 51 and 55 attached to the hollow inner casing 10', the electrically-conductive terminal ends 52 and 56 of contacts 51 and 55 being preferably disposed within the hollow interior of casing 10 nearer to one of the ends thereof; an internal magnetic slug 20 slidably disposed within casing 10 along central axis 13, one end of magnetic slug 20 having a permanently positioned North pole and the opposite end of a magnetic slug 20 having a permanently positioned South pole; an external permanent ring magnet means, e.g. ring magnet 30 positioned externally of hollow casing 10, preferably substantially surrounding hollow casing 10, said external ring magnet means 30 being generally perpendicular to central axis 13, one end of said external ring magnet means 30 having a permanently positioned North pole and the opposite end of external ring magnet means 30 having a permanently positioned South pole, the first end of slug 20 being of opposite polarity to that of the first end of external ring magnet means 30; and means to provide relative longitudinal movement between slug 20 and external ring magnet means 30 whereby when the magnetically neutral transverse meridian C of slug 20 approaches the external magent first end 31 and passes the magnetically neutral transverse meridian C of ring magnet means 30, slug 20 is repelled abruptly along the central axis 13 to govern the flow of electrical current between electrical contacts 51 and 55.

Representative embodiment 9 of the magnetically operable switch is illustrated in FIGURES 1-3. Switch embodiment 9 comprises a generally cylindrical hollow shell member 40 surroundably enclosing inner casing 10'. The lower second end 42 of shell 40 has a central opening, and second end 42 includes a downwardly-extending threaded nipple 4-3 which communicates with the interior of shell 46. Shell member 40 is a stationary member and is fixedly attached to a panel board 49 therebeneath having a threaded perforation, nipple 43 being threadedly engaged with panel board 49. The structural material of shell member 40 and for inner casing 10 is of low magnetic permeability, as for example, glass, resins, or nonferrous metal. By magnetically permeable material is meant that along which magnetic lines of flux tend to travel or shunt, as for example, ferrous, nickelous, and cobaltous materials, and magnetically impermeable denotes those materials, e.g. resins, glass, etc, that will not appreciably shunt or divert therethrough magnetic lines of flux.

External permanent ring magnet means e.g. ring magnet 30, is disposed within shell 40 and fixedly attached thereto, herein attached to the interior surface of shell member 40. For reasons to be explained later, external magnet 30 is preferably of an annular ring configuration so as to completely surround magnetic slug 20", and external magnet 30 is generally perpendicular to longitudinal central axis 13. External magnet 30 is of the permanent magnet type having a permanently positioned North pole at one end (herein at the lower second end 32) and having a permanently positioned South pole at the opposite end (herein at the upper first end 31). External magnet 30 has a magnetically neutral transverse meridian C between polar ends 31 and 32, the maximum lateral extension of magnetic flux for magnet 30 being at meridian C. Meridian C is desirably perpendicular to central axis 13.

Inner casing 10 is of generally cylindrical hollow configuration having an upper first end 11 and a lower second end 12, said transverse ends 11 and 12 being substantially perpendicular to central axis 13. The second end 12 of casing 10 includes an integral shank 16 that extends downwardly through nipple 43 and panel board 49 along axis 13. The lower end of shank 16 includes an integral flange 17 having an upper end 18. A bushing 44 having a longitudinal bore is engaged, as by friction, within nipple 43; the lower extremity 45 of bushing 44 is positioned within nipple 43 above the lower extremity thereof. Shank 16 is adapted to slide along the longitudinal bore of stationary bushing 44, and thus inner casing 10 is adapted to move along central axis 13. Flange 17 is wider than nipple 43, and its upper end 18 is adapted to abut the lower end 46 of nipple 43; thus, the length of shank 16 between casing second end 12 and flange upper end 18 governs the degree of movement for inner casing 10 along central axis 13. A plurality of distinctly separated electrical contacts is attached to elongate tubular casing 10. For example, a pair of contacts 51 and 55 pierce the casing upper first end 11 and are firmly secured to the casing structural material. The electrically-conductive terminal ends 52 and 56, respectively, of contacts 51 and 55 are disposed within the hollow interior of casing 10, and preferably, terminal ends 52 and 56 lie within a common plane substantially perpendicular to central axis 13. Casing upper end 11 includes a stabilizing means 19, herein as a block of iron or other magnetically permeable substance, the contacts terminal ends 52 and 56 being disposed below the lower extremity of stabilizer block 19. There are resiliently distensible spring means to norm-ally urge casing 10 downwardly so that its lower end 12 will normally abut the lower end 42 of shell member 40. The spring means may take the form of a pair of leaf springs 61 and 65, the lower end of said respective leaf springs being attached to casing 10 as by means of contacts 51 and 55, the upper end of said respective leaf springs resiliently bearing against the upper first end 41 of shell member 40. There are external electrical leads 71 and 75 adapted to carry external power to switch contacts 51 and 55; external leads 71 and 75 herein pass through shell member first end 41 and are conected to the electrically-conductive metallic leaf springs 61 and 65, said leaf springs providing a typical means of electrically connecting the leads 71 and 75 to contacts 61 and 62.

Disc-like magnetic slug 20 is slidably disposed within casing 10 and assumes a primary station against the lower second end 12 thereof when the casing 10 is in the vertically upright position shown. Magnetic slug 20 preferably has planar first and second ends that are substantially perpendicular to central axis 13. Magnetic slug 20 is preferably of similar cross-section to the interior cross-section of the casing 10, the lateral confines of the two being desirably of linearly generated configuration e.g. cylindrical. Further, the cross-sectional size of the slug 20 is slightly smaller than that of the casing interior so that the slug 20 will remain slidably perpendicular to central axis 13 without binding within casing 10. In other words, the slug first end 21 is always disposed nearer to casing first end 11 than to casing second end 12.

Slug 20 is a permanent magnet having a permanently positioned North pole at one end (herein at the upper first end 21) and having a permanently positioned South pole at the other end (herein at the lower second end 22). That end of slug 20 adjacent to contact ends 52 and 56 must be provided with electrically-conductive means. Although the structural material of metallic permanent magnets is normally electrically conductive, the end adjacent to the contacts must be free of electrically-insulative contaminants. Preferably, the slug end adjacent to the contacts is smoothly planar to simultaneously engage both contacts 51 and 55. In the case of non-conductive sinteredoxide permanent magnets, said adjacent end (herein at slug first end 21) may be provided with a thin integral layer 23 of copper or other metal especially suitable for electrical conductivity. Magnetic slug 20 has a magnetically neutral transverse meridian C between polar ends 21 and 22, the maximum lateral extension of magnetic flux for slug 20 being at meridian C. Meridian C is desirably perpendicular to central axis 13.

Operation of switch embodiment 9 is as follows. As shown in solid line in FIGURE 2, the external magnet 30 has a normal station wherein its transverse meridian C is spaced a given finite distance from the transverse meridian C of magnetic slug 20 when at its primary station against casing lower end 12. Because second end 32 is the proximal end of magnet 30 with respect to the first or upper end 21 of slug 20, and since the polarities of ends 32 and 21 are identical (herein both being North), the repellant magnetic forces of slug 20 and external magnet 30 tend to maintain slug 20 at its lower primary station. The combination of flanged shank 16, which is integrally connected to casing 10, and the nipple 43 furnish means to provide relative movement between slug 20 and external magnet 30 along central axis 13 to diminish the given finite distance between the transverse meridians C and C and cause slug transverse meridian C to approach external magnet first end 31 and to pass external magnet transverse meridian C; whereupon the repellant magnetic forces of slug 20 and external magnet 30 abruptly repel slug 20 to its secondary station, shown in phantom line in FIGURE 2, to simultaneously engage its electrically conductive layer e.g. 23, across contact ends 52 and 56. Specifically, as the flanged portion 17 of shank 16 is moved upwardly, either mechanically or manually, shank 16 and associated casing 10 move along central axis 13 until flange upper end 18 abuttably engages the lower extremity of nipple 43. The allowable relative movement between slug 20 and external magnet 30 must at least equal the distance between the slug primary station and the external magnet normal station i.e. the distance CC shown in solid line, and accordingly, the downwardly extending length of shaft 16 to flange upper end 18 is at least equal to the distance C-C. As flanged shaft 16 moves upwardly, the slug 20 contained within casing 10 at end 12' also moves upwardly, to diminish the distance between slug 20 and external magnet 30. As transverse meridian C of slug 20' so approaches external magnet first end 31, and crosses transverse meridian C, the first end 31 becomes the proximal end of magnet 30 with respect to slug first end 21, and thus the mutually repellant magnetic forces of slug 20 and external magnet 30 abruptly repel slug 20' upwardly a greater distance than the degree of upward movement for casing 10. If at least those areas of the electrically-conductive portion e.g. 23, between contact terminal ends 52 and 56 are adapted to simultaneously engage said contact ends 52 and 56, an electrically conductive bridge results between contacts 51 and 55.

Although the mutually repellant magnetic forces between magnets 20 and 30 will tend to maintain slug 20 as an electrically-conductive bridge across contacts 51 and 55, the presence of a supplemental stabilizing means will improve the shock and vibration resistance for the switch. For example, the supplemental stabilizing means may be as a block 19 of iron or other magnetically permeable metal attached to casing 10 adjacent to contacts 51 and 55, the lower end of stabilizer "block 19 being located above contact ends 52 and 56 so as not to interfere with the abutment of slug 20 with contact ends 52 and 56.

To break the circuit across contacts 51 and 55, it is necessary to translate slug 20 from its secondary station across contact ends 52 and 56 (shown in phantom line in FIGURE 2) to its primary station nearer to casing second end 12 (shown in solid line in FIGURE 2). To accomplish this task, shank 16 is moved downwardly to its limit of travel, herein when casing second end 12 abuts shell lower end 42. During this downward travel, slug 20 remains at its second station across contact ends 52 and 56 until, as shown in dotted line in FIGURE 2, the transverse meridian C of slug 20 crosses transverse meridian C toward external magnet second end 32; at this point, second end 32 once again becomes the proximal end of magnet 30 with respect to slug first end 21, the magnetically repe'llant forces of magnets 20 and 30 repelling slug 20 to its primary station, thus breaking the circuit between contacts 51 and 55. In order to alternatively make and break the circuit between contacts 51 and 55, it is essential that the distance between the primary and secondary stations for slug 20. be less than the given finite distance C-C' between the external magnet normal position and the slugprimary station, as shown in solid line of FIGURE 1. Accordingly, the degree of relative movement between magnets 20 and 30, as by the reciprocating movement of casing 10, must exceed the said given finite distance C-C'.

In order to exert the maximum possible magnetic forces upon magnetic slug 20, it is desirable that magnets 20 and 30 be positioned as close as possible to each other, both laterally and longitudinally e.g. the distance C-C'. Further, the external magnet means 30 should preferably substantially surround magnetic slug 20; accordingly, either several separate bar magnets having transversely aligned meridians should be spaced at intervals about the lateral periphery of casing 10, or a single annular ring magnet should surround the lateral periphery of casing 10. If a single annular ring magnet is employed, its transverse meridian C should of course be positioned in parallelism to the transverse meridian C of slug 20 in order that slug 20 may slide freely along casing 10. The magnetic strength for external magnet 30 must be sufficiently great to repel slug '20 and to overcome the resistance of a stabilizer block e.g. 19, if such a stabilizing means is so employed.

The magnetically operable switch 99 of FIGURE 4 is identical in magnetic principle to switch 9 of FIGURE 2. However, the electrical contacts Hand 55 are adjacent to the slug primary station at casing second end 12, rather than the slug secondary station, so that switch 99 is normally closed rather than normally open as is switch 9. Further, in direct counterdistinction to switch 99, the relative movement between slug 20 and external magnet 36) is provided by holding casing stationary and by moving shell member 40 downwardly. Thus, slug second end 22 carries the electrically-conductive portion e.g. 23. Also, leads 71 and 75 for contacts 51 and 55, respectively, may conveniently intersect shell second end 42 and shaft flange 17, rather than shell first end 41; leads 71 and l 75 are preferably flexibly undulate as indicated, appropriate to the reciprocatable movement of shell member 40 along central axis 13. Casing 10 may be held elevated upon riser-like protruberances 77 to accommodate leads 71 and 75 between casing 10 and shell member 40. Protuberances 77 may be of a resilient material to protect slug from shock and vibrational forces at its primary station.

Shankfiange 17, rather than nipple 43, is threaded and flange 17 is threadedly engaged with panel board 49. Helical spring 82, surrounding shaft 16, provides resiliently distensible means between nipple 43 and its conterminous bushing 44 and flange 17. Shell member 40 may travel downwardly until nipple 43 abuts flange 17, as indicated in phantom line in FIGURE 4. When shell 40 and its integral external magnet move downwardly, so that transverse meridian C of magnet 30 crosses transverse meridian C of slug 20 toward slug second end 22, slug 20 is abruptly repelled upwardly toward its secondary station, thus breaking the circuit between contacts 51 and 55. As with switch embodiment 9, the degree of relative movement between shell (including its integral permanent ring magnet means 30) and slug 20 is greater than the given finite distance between the transverse meridians C and C when magnet 30 is at its normal station and when slug 20 is at its primary station, as indicated in solid line in FIGURE 4. As with the switch 9 embodiment, an opposite degree of relative movement between slug 20 and external magnet 30 will, when transverse meridian C' of magnet 30 crosses transverse meridian C of slug 20 toward slug first end 21, return slug 20 to its primary station to normally close the contacts 51 and 55. Stabilizer block 19 may be employed at one or both ends of casing 10, to protect slug 20 from shock and vibrational forces.

With both the 9 and 99 embodiments, there may be holding means to set or maintain the secondary station position of slug 20. For example, a lever or toggle may be employed, to hold" the upward position of casing 10 in switch embodiment 9 or the downward position of shell 40 in switch embodiment 99.

Preferably, casing 10 is of a gas-impervious construction, including appropriate seals at contacts 51 and 55, so that the casing may be filled with nitrogen or other inert atmosphere to provide an sparkless explosion-proof switch device.

The alternate bridging element 28 of FIGURE 5 comprises the disc-like permanent magnet portion 20 including an upper first end 21 and a lower second end 22. The electrically-conductive metallic strip 23 is joined to first end 21 with an intervening resinous layer 29. Layer 29 has a constricted portion having a narrower crosssection than that for strip 23 so that strip 23 is resiliently flexible with respect to the permanent magnet sl-ug 20 to insure etfecive abutment with contact ends 52 and 56 in the event the common plane of 52 and 56 is not substantially parallel with electrically-conductive layer 23.

From the foregoing, the construction .and operation of the magnetically operable switch will be readily understood and further explanation is believed to be unnecessary. However, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the appended claims.

I claim:

1. A magnetic slug switch to control the flow of electrical current between at least two of a plurality of distinctly separated electrical leads, said magnetic slug switch comprising:

(A) A tubular hollow casing having a longitudinal central axis, an upper first end and a lower second end both ends being transversely disposed with respect to the casing longitudinal axis, said tubular hollow casing together with its longitudinal central axis being substantially vertically disposed, the upright longitudinal walls of said tubular casing being provided of a structural material that is of low magnetic permeability;

(B) A magnetic slug disposed internally within said hollow casing, said magnetic slug having an upper first end located nearer to the casing upper first end, said magnetic slug having a lower second end located nearer to the casing lower second end, said magnetic slug having a permanently positioned magnetic North pole at one end thereof and a permanently positioned magnetic South pole at the other end thereof, said magnetic slug having a magnetically neutral transverse meridian between the first and second ends thereof, the cross-sectional size of the magnetic slug being slightly less than the cross-sectional size of the tubular casing hollow interior whereby the magnetic slug is vertically slidably disposed within the tubular casing along the longitudinal central axis thereof so that the slug upper first end is always nearer to the casing upper first end than is the slug lower second end, said magnetic slug having two stations within the casing including a primary station at the lower extremity of its longitudinal travel and a second station at the upper extremity of its longitudinal travel, the magnetic slug being normally positioned at its lower primary station located nearer to the lower second end of the said magnetic slug having a lower second end located nearer to the casing lower second end, said magnetic slug having a permanently positioned magnetic North pole at one end thereof and a permacasing than to the upper first end of the casing when nently positioned magnetic South pole at the other the casing is so vertically disposed; a plurality of disend thereof, said magnetic slug having a magnetically tinctly separated electrical leads attached to the neutral transverse meridian between the first and tubular casing, said electrical leads having terminal second ends thereof, the cross-sectional size of the ends within the tubular casing between the upper magnetic slug being slightly less than the cross-secfirst end of the casing and the upper first end of the 10 tional size of the tubular casing hollow interior wheremagnetic slug; the upper first end of said magnetic by the magnetic slug is vertically slidably disposed slug having a structurally continuous electrical conwithin the tubular casing along the longitudinal cenductor portion adapted to simultaneously engage at tral axis thereof so that the slug upper first end is least two of said distinctly separated electrical leads always nearer to the casing upper first end than is the when the magnetic slug is at its upper secondary slug lower second end, said magnetic slug having station; two stations within the casing including a primary (C) An external magnet disposed externally of said station at the lower extremity of its longitudinal travel tubular casing, said external magnet having an and a second station at the upper extremity of its upper first end and a lower second end, the exlongitudinal travel, the magnetic slug being norternal magnet second end being located nearer g0 mally positioned at its lower primary station located to the casing second end than is the external magnet nearer to the lower second end of the casing than to first end, said external magnet having a permanently the upper first end of the casing when the casing is positioned North pole at one end thereof and a perso vertically disposed; a plurality of distinctly sepmanently positioned South pole at the other end arated electrical leads attached to the tubular casthereof, the magnetic polarity of the external maging, said electrical leads having terminal ends withnet first end being identical to the magnetic polarity in the tubular casing between the lower second end of the slug second end, the magnetic polarity of the of the relatively fixed casing and the lower second external magnet second end being identical to the end of the magnetic slug; the lower second end of magnetic polarity of the slug first end, said external said magnetic slug having a structurally continuous magnet having a magnetically neutral transverse electrical portion adapted to simultaneously engage meridian between the first and second ends thereof, at least two of said distinctly separated electrical leads said external magnet providing a relatively fixed when the magnetic slug is at its lower primary station; normal station wherein the external magnettrans- (C) An external magnet disposed externally of said verse meridian is spaced a given finite distance from tubular casing said external magnet having an upper the transverse meridian of the magnetic slug and first end and a lower second end, the external magalso between the transverse meridian of the magnetic net second end being located nearer to the casing slug at its lower primary station and the casing first second end than is the external magnet first end, end whereby the mutually repellent magnetic forces said external magnet having a permanently posiof the slug and external magnet maintain the slug tioned North pole at one end thereof and a permaat its lower primary station, the distance between the nently positioned South pole at the other end thereof, primary and secondary stations for the slug within the magnetic polarity of the external magnet first end the casing being less than said given finite distance, being identical to the magnetic polarity of the slug and second end, the magnetic polarity of the external (D) Means to provide movement of the casing along magnet second end being identical to the magnetic its longitudinal central axis toward the external magpolarity of the slug first end, said external magnet net upper first end to cause the magnetically neutral having a magnetically neutral transverse meridian transverse meridian of the slug to approach the exbetween the first and second ends thereof, said external magnet lower second end and to pass the magternal magnet providing a relatively fixed normal netically neutral transverse meridian of the external first station wherein the external magnet transverse magnet whereby the mutually repellant magnetic 0 meridian is spaced a given finite distance from the forces of the slug and external magnet abruptly repel transverse meridian of the magnetic slug at the magthe slug to its upper secondary station against the netic slug primary station toward the casing first end terminal ends of at least two of said distinctly sepwhereby the mutually repellant magnetic forces of arated electrical leads, the degree of relative movethe slug and external magnet maintain the slug at its ment between the movable casing and external magprimary station, the distance between the primary net exceeding said given distance whereby an oppoand secondary stations for the slug within the casing site degree of relative movement between the casing being less than said given finite distance, and and external magnet will return the slug to its lower (D) An exterior shell member surroundably enclosing primary station. the tubular hollow casing and the external magnet, 2. A magnetic slug switch to control the fiow of elec- 30 said external magnet being attached to the interior side trical current between at least two of a plurality of disof the shell member, said shell member being resilienttinctly separated electrical leads, said magnetic slug switch ly attached to the tubular casing to permit reciprocatcomprising: ing movement of the shell member with respect to (A) A relatively fixed tubular hollow casing having a the tubular casing longitudinal axis, said shell memlongitudinal central axis, an upper first end and a 5 ber providing means to move the external magnet lower second end both ends being transversely disalong the casing longitudinal axis toward the casing posed with respect to the casing longitudinal axis, lower second end to cause the magnetically neutral said tubular hollow casing together with its longimeridian of the external magnet to approach the tudinal central axis being substantially vertically slug upper first end and to pass the magnetically disposed, the upright longitudinal walls of said tubu- 7 neutral transverse meridian of the slug whereby the lar casing being provided of a structural material mutually repellant magnetic forces of the slug and that is of low magnetic'permeability; external magnet abruptly repel the slug to its upper (B) A magnetic slug disposed internally within said secondary station remote of the terminal ends of at hollow casing, said magnetic slug having an upper least two of said distinctly separated electrical leads, first end located nearer to the casing upper first end, the degree of relative movement between the casing and external magnet exceeding said given distance whereby an opposite degree of movement between the movable external magnet and the stationary casing will return the slug to its lower primary station, said tubular casing second end including means extending longitudinally through the shell member to maintain said tubular casing stationary relative to the shell member.

3. The magnetically operable switch of claim 1 wherein the elongate casing and the external magnet are enclosed within an exterior shell member, said shell member having a permanent ring-shaped magnet attached to the interior side thereof; wherein the elongate casing is attached to the shell member with resiliently distensible means to permit reciprocating movement of the casing within the shell along the longitudinal axis of the casing whereby the tubular casing is normally urged downwardly of the exterior shell so that the first end of the slug at its primary station is positioned below the second end of the external magnet; wherein there are electrical leads for the respective electrical contacts of the elongate casing, said electrical leads passing through the shell member; and wherein the casing second end includes a longitudinal shaft extending downwardly through the shell member second end.

4. The magnetically operable switch of claim 3 wherein the elongate casing includes a stabilizing means adjacent to the terminal ends of the electrical contacts.

-5. The magnetically operable switch of claim 1 wherein the elongate casing includes a stabilizing means adjacent to the terminal ends of the electrical contacts.

6. The magnetically operable switch of claim 4 wherein the tubular casing is of elongate cylindrical configuration having closed first and second ends; wherein the exterior shell member is of cylindrical configuration having a substantially closed upper first end and a centrally perforate lower second end, the casing longitudinal shaft extending through the central perforation of the shell member second end parallel to the casing longitudinal central axis; wherein terminal ends of the electrical contacts are co-planar and extend into the tubuar casing nearer to the upper first end thereof; wherein the stabilizing means comprises a magnetically permeable metallic block that extends into the casing first end a distance less than that for the electrical contacts terminal ends; wherein the magnetic slug comprises a distinct laminar strip of electrically-conductive metal attached at the first end thereof,

said laminar strip having a substantially planar first end 10 and a breadth exceeding the spacing between the electrical contacts terminal ends.

7. The magnetically operable switch of claim 5 where in the tubular casing is of elongate cylindrical configuration having closed first and second ends; wherein the exterior shell member is of cylindrical configuration having a substantially closed upper first end and a centrally perforate lower second end, the casing longitudinal shaft extending through the central perforation of the shell member second end parallel to the casing longitudinal central axis; wherein terminal ends of the electrical contacts are co-planar and extend into the tubular casing nearer to the second end thereof; wherein the stabilizing means comprises a magnetically permeable metallic block that extends into the casing second end a distance less than that of the electrical contacts terminal ends; wherein the magnetic slug comprises a distinct laminar strip of electrically-conductive metal attached at the lower second end thereof, said laminar strip having a substantially planar second end and a lateral breadth exceeding the spacing between the electrical contacts terminal ends.

8. The magnetically operable switch of claim 6 wherein the shell member is attached to a panel board; wherein there are holding means to atfix the longitudinal position of the reciprocatable tubular casing; and wherein the distinct laminar strip of electrically-conductive metal is resiliently attached to the magnetic slug.

9. The magnetically operable switch of claim 7 wherein the tubular casing is attached to a panel board; wherein there are holding means to affix the longitudinal position of the reciprocatable shell member; and wherein the distinct laminar strip of electrically-conductive metal is resiliently attached to the magnetic slug.

References Cited UNITED STATES PATENTS 3,016,434 1/1'962 Seeger 20087 3,025,372 3/1962 Benson 200 67 3,260,821 7/1966 Yokoo 20087 3,243,238 3/1966 Lyman 3-0 8l0 OTHER REFERENCES 1,141,000, 12/ 1962, Zuckschwerdt (German printed application) 1 Sht. Dwg., 2 pp. spec. 335-205.

BERNARD A. GILHEANY, Primary Examiner. R. N. ENVALL, JR., Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTTON Patent No. 3,376,527 April 2, 1968 George Risk It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 9, line 29, the claim reference numeral "1" should read 2 Signed and sealed this 7th day of October 1969.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR.

Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer 

1. A MAGNETIC SLUG SWITCH TO CONTROL THE FLOW OF ELECTRICAL CURRENT BETWEEN AT LEAST TWO OF A PLURALITY OF DISTINCTLY SEPARATED ELECTRICAL LEADS, SAID MAGNETIC SLUG SWITCH COMPRISING: (A) A TUBULAR HOLLOW CASING HAVING A LONGITUDINAL CENTRAL AXIS, AN UPPER FIRST END AND A LOWER SECOND END BOTH ENDS BEING TRANSVERSELY DISPOSED WITH RESPECT TO THE CASING LONGITUDINAL AXIS, SAID TUBULAR HOLLOW CASING TOGETHER WITH ITS LONGITUDINAL CENTRAL AXIS BEING SUBSTANTIALLY VERTICALLY DISPOSED, THE UPRIGHT LONGITUDINAL WALLS OF SAID TUBULAR CASING BEING PROVIDED OF A STRUCTURAL MATERIAL THAT IS OF LOW MAGNETIC PERMEABILITY; (B) A MAGNETIC SLUG DISPOSED INTERNALLY WITHIN SAID HOLLOW CASING, SAID MAGNETIC SLUG HAVING AN UPPER FIRST END LOCATED NEARER TO THE CASING UPPER FIRST END, SAID MAGNETIC SLUG HAVING A LOWER SECOND END LOCATED NEARER TO THE CASING LOWER SECOND END, SAID MAGNETIC SLUG HAVING A PERMANENTLY POSITIONED MAGNETIC NORTH POLE AT ONE END THEREOF AND A PERMANENTLY POSITIONED MAGNETIC SOUTH POLE AT THE OTHER END THEREOF, SAID MAGNETIC SLUG HAVING A MAGNETICALLY NEUTRAL TRANSVERSE MERIDIAN BETWEEN THE FIRST AND SECOND ENDS THEREOF, THE CROSS-SECTIONAL SIZE OF THE MAGNETIC SLUG BEING SLIGHTLY LESS THAN THE CROSS-SECTIONAL SIZE OF THE TUBULAR CASING HOLLOW INTERIOR WHEREBY THE MAGNETIC SLUG IS VERTICALLY SLIDABLY DISPOSED WITHIN THE TUBULAR CASING ALONG THE LONGITUDINAL CENTRAL AXIS THEREOF SO THAT THE SLUG UPPER FIRST END IS ALWAYS NEARER TO THE CASING UPPER FIRST END THAN IS THE SLUG LOWER SECOND END, SAID MAGNETIC SLUG HAVING TWO STATIONS WITHIN THE CASING INCLUDING A PRIMARY STATION AT THE LOWER EXTREMITY OF ITS LONGITUDINAL TRAVEL AND A SECOND STATION AT THE UPPER EXTREMITY OF ITS LONGITUDINAL TRAVEL, THE MAGNETIC SLUG BEING NORMALLY POSITIONED AT ITS LOWER PRIMARY STATION LOCATED NEARER TO THE LOWER SECOND END OF THE CASING THAN TO THE UPPER FIRST END OF THE CASING WHEN THE CASING IS SO VERTICALLY DISPOSED; A PLURALITY OF DISTINCTLY SEPARATED ELECTRICAL LEADS ATTACHED TO THE TUBULAR CASING, SAID ELECTRICAL LEADS HAVING TERMINAL ENDS WITHIN THE TUBULAR CASING BETWEEN THE UPPER FIRST END OF THE CASING AND THE UPPER FIRST END OF THE MAGNETIC SLUG; THE UPPER FIRST END OF SAID MAGNETIC SLUG HAVING A STRUCTURALLY CONTINUOUS ELECTRICAL CONDUCTOR PORTION ADAPTED TO SIMULTANEOUSLY ENGAGE AT LEAST TWO OF SAID DISTINCTLY SEPARATED ELECTRICAL LEADS 